1. Field of the Invention
The present invention relates to a phase measurement and control system for aiming and focusing a laser beam in response to the time-varying phase thereof, but more specifically, it relates to a system for measuring the transverse phase pattern of the laser beam using laser field intensity measurements.
2. Description of the Prior Art
It is known that the spatial phase variations of laser beams are currently measured using scanning interferometers. However, scanning interferometers are expensive and difficult to adjust and maintain under field conditions outside a laboratory environment. Additionally, the operations of these instruments are compromised by temporal variations of phase of the entire laser beam. Also, purely computational techniques for determining the phase distribution of the laser beam have produced ambiguous results.
Accurate measurements of laser beam phase variations in a transverse plane are required, for example, in adaptative transmission systems in order to better aim and focus the laser beam in hostile environments. In these systems, laser beam degradation is avoided and beam aiming and focusing is generally accomplished by electro-mechanical variations of a plurality of mirror segments of a multi-dither mirror in order to correct for laser spatial phase variations. Since these variations change with time, the multi-dither mirror must be continuously adjusted in response to the time-varying phase of the laser beam.
The prior art, as indicated hereinabove, include advances in spatial phase measurements of a laser beam. However, insofar as can be determined, no prior art phase measurement system incorporates all of the features and advantages of the present invention.